Regretfully, the claim that HMS Tetrarch was found off Tabarka is just a hoax (so are all the other claims that the same author made, i.e. that he found 8 or 9 submarine wrecks in the same spot without providing a single proof). HMS Tetrarch was probably mined off Sicily as her route seems to indicate. No compelling reason for this submarine and the others to go to Tabarka which was a fishing village of no importance at the time (and not a single reference in Allied or Axis submarine sailing orders or signals that would indicate any interest in investigating Tabarka). Even during the Axis occupation of Tunisia, Tabarka was not used by the belligerents as it was too close to Allied airfields in Algeria. A minefield was laid there in late April 1943 but this was to protect the Axis evacuation from Allied MTBs operating from Bone and, AFAIK, it caused no casualties.

Regarding your interest in S-boats operations, the same individual who claimed to have found HMS Tetrarch also claimed to have found S 35 a few miles from Tabarka.

I wonder what is your view on this story?

My views are that this is also a hoax as S 35 was lost north of Ras El Doukara (or Ras Enghela) that is over 40 mlles from Tabarka. Wreckage were found by other S-boats indicating she was lost on a drifting mine (possibly from minefield laid by HMS Abdiel on 28 February 1943).